1. Field of the Disclosed Subject Matter
The present disclosed subject matter relates to cyclone assemblies, and particularly stabilizer assemblies to secure and stabilize cyclone assemblies within a multi-phase reaction bed vessel.
2. Description of Related Art
Fluid catalytic cracking (FCC) processes are used for petroleum and petrochemical conversion processes. These processes can provide efficient and selective catalytic cracking of hydrocarbon-containing feedstock. For example, small catalyst particles can be fluidized and mixed with a feedstock by intimate contact under thermally active conditions to generally produce lower molecular weight “cracked” products. FCC processes are beneficial due at least in part to the ability to continuously recycle and regenerate the spent catalysts and to process large volumes of hydrocarbon-containing feedstock.
In FCC processes, higher molecular weight feeds contact fluidized catalyst particles, most advantageously in the riser reactor of the fluidized catalytic cracking unit. Contact between feed and catalyst can be controlled according to the type of product desired. In catalytic cracking of the feed, reactor conditions, including temperature and catalyst circulation rate, can be adjusted to increase formation of the desired products and reduce the formation of less desirable products, such as light gases and coke.
Various fluidized catalytic cracking reactor riser and reactor vessel designs can be utilized. For example, certain fluidized catalytic cracking reactors utilize a short contact-time cracking configuration. With this configuration, the catalyst contacts the fluidized catalytic cracker feedstream for a limited time in order to reduce excessive cracking, which can result in the increased production of less valued products such as light hydrocarbon gases, as well as increased coking deposition on the cracking catalysts.
Certain fluidized catalytic cracking configurations utilize a reactor riser cracking configuration wherein the catalyst can contact the fluidized catalytic cracker feedstock in a reactor riser, and the catalyst and the hydrocarbon reaction products can be separated shortly after the catalyst and hydrocarbon mixture flows from the reactor riser into the fluidized catalytic cracking reactor. Many different fluidized catalytic cracking reactor designs are known. For example, certain designs utilize mechanical cyclones internal to the reactor to separate the catalyst from the hydrocarbon reactor products. This separation process can reduce post-riser reactions between the catalyst and the hydrocarbons as well as separate the cracked hydrocarbon products for further processing from the spent catalyst, which can be regenerated and reintroduced into the reaction process.
Mechanical cyclone assemblies generally can include a plurality of cyclones joined together and secured to the pressure vessel of the reactor. An insufficiently balanced and supported cyclone system can produce a vibration frequency, which can promote metal fatigue and lead to mechanical failure. A plurality of flat plate hanger straps typically are utilized to support one or more of the cyclones to the pressure vessel. However, the conventional hanger strap support system can be challenging to engineer, particularly to provide support points for uniformly balancing the cyclone system. An unbalanced cyclone system can cause an axial tilt of one or more cyclones, which can depreciate the overall cyclone system stability and performance during the system run cycle. Additionally, an increased length of the hanger straps can lead to increased thermal expansion during system operation. Hanger straps exceeding a desired length can lead to over-expansion of one or more of the cyclones, which can cause an axial tilt of the cyclone system and thus inefficiencies.
Cyclone systems can be further stabilized from vibration by restraining the dipleg conduits of the cyclones from movement. In practice, cyclone pairs can be joined to other cyclone pairs by one or more braces. For example, braces can be used to join three cyclones in a triangular fashion. However, certain cyclone arrangements can be unsuitable for such a triangular integration, for example if fewer than three cyclones are employed. Furthermore, space limitations and interference from other hardware can restrict the area available to form a desired bracing arrangement. In addition, non-uniform thermal movement between the pressure vessel shell and the cyclone system can reduce the effectiveness of such a bracing arrangement.
As such, there remains a need for improved assemblies and methods to secure and stabilize cyclone assemblies in a reaction bed vessel.